Primary Productivity (College Board AP® Environmental Science): Flashcards
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Define primary productivity.
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Define primary productivity.
Primary productivity is the rate at which biomass is produced using an external energy source (like sunlight) and inorganic sources of carbon and other elements.
What energy conversion do primary producers carry out during photosynthesis?
During photosynthesis, primary producers convert light energy into chemical energy, which is stored in biological molecules (biomass).
Define gross primary productivity (GPP).
Gross primary productivity (GPP) is the rate at which plants store chemical energy or biomass via photosynthesis in a given area over time.
True or False?
GPP includes energy that the plant later uses for its own metabolic needs.
True.
GPP represents the maximum energy available before any is used by the plant for its metabolic needs, such as respiration.
Define net primary productivity (NPP).
Net primary productivity (NPP) is the rate at which energy is stored in plant biomass, allowing for respiratory losses.
What is the equation for net primary productivity?
NPP = GPP - R, where R is plant respiratory losses.
Why is NPP important in an ecosystem?
NPP is the energy available to higher trophic levels, such as primary consumers and decomposers, so it forms the basis of food chains and food webs.
In agricultural systems, NPP can be thought of as the plant growth that can be harvested by .
In agricultural systems, NPP can be thought of as the plant growth that can be harvested by farmers.
What four factors mainly drive differences in NPP between ecosystems?
Differences in NPP are driven mainly by sunlight, temperature, water, and nutrients (especially nitrogen and phosphorus).
Which two ecosystems are the most productive?
The most productive ecosystems are tropical rainforests and estuaries.
True or False?
The open ocean has low NPP per m² because it is light-limited.
False.
The open ocean is nutrient-limited, not light-limited, because nutrients sink below the sunlit surface layer. Its vast area still makes a major contribution to total global NPP.
Why is the tundra one of the least productive ecosystems?
The tundra is one of the least productive ecosystems because it is cold-limited with a very short growing season.
In what energy units can GPP and NPP be expressed?
GPP and NPP can be expressed as energy per unit area per unit time, for example J m⁻² yr⁻¹ (joules per square meter per year).
True or False?
GPP and NPP can only be expressed in units of energy.
False.
GPP and NPP can also be expressed as mass per unit area per unit time, for example g m⁻² yr⁻¹ (grams per square meter per year).
How may GPP and NPP be measured in aquatic environments?
In aquatic environments, GPP and NPP may be measured per unit volume, for example kg m⁻³ yr⁻¹ (kilograms per cubic meter per year).
In aquatic ecosystems, light is absorbed within the upper 1 meter of water.
In aquatic ecosystems, red light is absorbed within the upper 1 meter of water.
How deep does blue light usually penetrate in clear water?
Blue light penetrates deeper than red light, but usually no more than 100 meters in clear water.
How are aquatic photosynthesizers such as phytoplankton adapted to low light levels?
Some aquatic photosynthesizers have pigments like chlorophyll-a that absorb light more efficiently, while others live near the surface to maximize light exposure.
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